The invention relates to a medical instrument, in particular a rectoscope, with a working insert which may be inserted into a coupling housing sitting on the proximal side on an instrument shank and is releasably connectable to said housing and which comprises a seal, carried by a carrier, which has at least one elastic socket for the sealed leading-through of auxiliary instruments and which seals a first axial passage formed in the carrier with respect to the coupling housing. Such a medical instrument is known from DE 33 19 049 C2.
With transanal endoscopic microsurgery (TEM) a maximum freedom of movement of TEM and auxiliary instruments introduced through the working insert into the instrument shank, a quicker and problem-reduced change of defect sealing elements as well as a quick removal possibility of resected tissue parts is demanded. Since the proximal ends of the three individual accesses formed in the working insert of the known endoscope in each case have a bulge-shaped thickening and over these bulge-shaped thickening elastic sealing sockets are pushed, by way of the restricted conditions problems with a TEM operation may occur. Furthermore with the known rectoscope the action radius and the movement freedom of the TEM instruments are restricted by tube connections. For removing operation preparations furthermore the complete working insert with the applied optics must be removed.
It is the object of the invention to provide a medical instrument according to the known type, in particular a rectoscope, which creates an access suitable for the extensive free movability of several TEM instruments and has a working insert with a large-lumened as possible instrument passage and with a quickly exchangeable and inexpensively manufacturable sealing element, suitable as a wearing part, on the instrument passage on which the sealing element can be simply locked and unlocked.
Proceeding from a medical instrument according to the known type and the type previously mentioned this object according to the invention is achieved in that the seal consists of a base body which is located in a holder and which with each socket forms a one-piece component of elastic material, and that the holder comprises means for the releasable connection to the carrier.
By way of the one-piece formation of the base body with the sockets the seal may excellently fulfill its sealing functions and it may, since it may be easily releasably fastened on the carrier, be advantageously manufactured as an inexpensive single-use or disposable article.
By way of the fact that the holder of the seal comprises means for the simply releasable connection to the carrier, the complete sealing element may be simply inserted into the carrier and again be released therefrom. If one unites the seal with the holder on manufacture to a one-piece component then the handling, i.e. the fastening and the removal of the seal with the holder onto and out of the carrier is simplified even further. The seal may, corresponding to the respective application purpose, be made available in differing variants which may only have a single or several elastic sockets for introducing several auxiliary instruments.
The first passage in the carrier preferably has a large-lumened crescent-shaped contour which matches with a distal-side attachment on the base body of the seal, and the socket or sockets projecting proximally from the base body end in a passage of the base body in the region of the attachment. With this embodiment form the holder encompassing the base body is likewise essentially crescent-shaped and formed in the manner of a bow. This bow has an axial opening whose contour is likewise crescent-shaped and thus corresponds to the crescent-shaped outer contour of the base body so that the holder may encompass the base body with a positive fit in the region of its attachment.
By way of its crescent-shaped contour the first passage offers a relatively large opening in the carrier, through which the used auxiliary instruments in the body cavity may be very well manipulated.
The attachment may, where it is enclosed by the holder, comprise an annular shoulder on which the holder lies. This annular shoulder may on its proximal-side shoulder surface comprise a crescent-shaped deepening which here accommodates the holder with a positive fit.
Preferably the two bow ends of the holder in each case comprise a recess such that the have a fork shape, by which means the holder with the bow ends may be easily releasably fastened with a positive and non-positive fit to fastening pegs projecting proximally from the end-side face of the carrier and tapering conically in the distal direction. The use of the bow-shaped holder with its fork-shaped formed ends simplifies the fastening and the simple releasability of the seal on the carrier since the fork-shaped ends only need to be suspended into the fastening peg and at the opposite side pressed against the end-side face of the carrier.
A second passage in the carrier serving for introducing an optic is provided at a distance from the first crescent-shaped passage such that the second passage lies free of the seal. By way of the crescent contour of the first passage in the carrier and the corresponding crescent shape of the seal and of the holder encompassing the seal thus the second passage in spite of the large-lumened first passage lies relatively tightly on the longitudinal axis of the medical instrument.
By way of the restoring force of the elastic material of the annular shoulder, of the seal, pressed against the proximal-side surface of the carrier and by way of the centering effect of the mentioned tapering of the fastening peg, a secure and also gas and fluid tight fastening of the seal on the carrier is achieved. On account of the relatively high friction which the elastic material from which the seal is manufactured comprises, the security of the fastening of the seal on the carrier is additionally increased and a lateral displacement of the seal on the carrier and a reduction of the sealing function is effectively prevented.